*Fresh tuna should be firm and flavorful. Bigeye tuna is moist and clean-tasting, truly rich in texture. Its flavor is more like meat than fish. It should have a deep ruby red color, and is best grilled or sautéed. It should never be overcooked, and is usually served rare. Another good variety is yellowfin, which is a lean meat but firm, with a large flake. It has a definite flavor of its own but is not too fishy, and should have a red color varying from a dark burgundy to a pale red.

One of my patients sends his housekeeper to Katagiri, a Japanese grocer and specialty store on East Fifty-ninth Street, to buy him only fresh sushi-quality tuna. They personally pick the fish from the Fulton Fish Market daily.

1. Mix all the marinade ingredients together and marinate the tuna steaks for 1 hour, turning once or twice. Keep the fish in the refrigerator while it soaks.

2. Grill over hot coals or on an oven grill for 5 minutes each side, basting with the marinade from time to time. Top with sesame seeds.